Ski glider



April 2, 1963 R. T. CELLA 3,033,933

SKI GLIDER Filed April 28, 1960 2 Sheets-Sheet l Inventor le/c/mea ZCELL/4 Attorney April 2, 1963 R. T. CELLA 3,033,933

SKI GLIDER Filed April 28, 1960 2 Sheets-Sheet 2 NORMAL WIND LINE Q! 0 kN no N CAMBC R LINE SUPPORT PO/ N T A Horn 2 y tates This inventionrelates to gliders and more particularly to a glider suited for use withwater skis.

An object is to provide a glider of the above type which is capable oflifting a skier from the water and returning him to the water withoutrequiring any action or control on his part.

Another object is to provide a device of the above type whichautomatically lifts the skier from the water when towed at apredetermined speed, attains a height which depends in general upon thetowing speed and which is capable of returning to the water in a freeglide should the towing force be interrupted as by the stopping of thetowing boat or the breaking of the tow line.

Another object is to provide a device of the above type which is notdependent for its safe operation upon any skill on the part of therider.

Other objects and advantages will be apparent as the nature of theinvention is more fully disclosed.

The invention provides a glider of the above type having a high degreeof lateral and longitudinal stability. When disturbed from its normalfree glide path as by a gust of wind, it will return to its free glideattitude in not more than two highly damped oscillations. Lateralstability is attained by providing a suitable wing dihedral.Longitudinal stability is attained by locating the weight of the riderat a predetermined point on the wing chord and suspending the rider froma pivot point so chosen that the center of gravity is located below thecenter of lift by the required amount to provide a righting momenttending to return the glider to its free glide attitude whenever theglide angle is disturbed. The pivotal suspension of the rider not onlycauses the weight to be applied constantly at the predetermined pivotpoint for producing the righting moment but also provides a safetyfactor as it prevents the rider from being thrown forward or backwarddue to a sudden change in the pitch angle of the glider.

The nature of the invention will be better understood from the followingdescription, taken in connection with the accompanying drawings in whicha specific embodiment has been set forth for purposes of illustration.

In the drawings:

FIG. 1 is a side elevation of a glider embodying the invention;

FIG. 2 is a broken top plan view of the glider;

FIG. 3 is an enlarged detail taken on the line 3-3 of FIG. 2 showing theconstruction of the supporting framework;

FIG. 4 is a section taken on the line 44 of FIG. 3;

FIG. 5 is a diagram illustrating the relationship of the variouscomponents of the glider;

FIG. 6 is a perspective view of the glider framework; and

FIG. 7 is a detail of the support bar.

Referring to the drawings more in detail the glider is shown as having awing 10 composed of a framework of tubular members of strong lightweight material such as aluminum which are joined together by welding,bolting or in any other convenient manner to form a rigid structure. Inthe form shown the framework comprises a series of cambered tubes 11shaped to conform to the wing surface and spaced along the length of thewing. The tubes 11 are joined at their leading ends to a tube 12extending along the leading edge of the wing 10 and at their trailingends to a tube 13 extending along the trailing edge of the wing. Atapered strip 14 is disposed in back of the tube 13 to shape thetrailing edge of the wing.

atet "ice The forward tube 12 extends substantially straight across theglider to points 15 near the wing tips, at which points it is bentupwardly at an angle of say 30 degrees to form a dihedral in the mannerwell known in the art. The rear tube 13 is similarly bent upwardly toform the dihedral and forwardly to conform to the desired shape of thewing tip. The entire structure is covered on both sides with a standardwing fabric 16 which is secured in place and stiffened with airplanedope as in the usual practice to form an air foil which is impervious towater so that the structure is buoyant. The center portion of the wingbetween the two central camber tubes 11 is left open to form an opening17 for the rider. A tube 30 extends between the two central camber tubes11 at the forward edge of the opening 17.

The framework or truss is formed by vertical struts 20 extendingdownwardly from the two central camber tubes 11 at a point aboutone-fifth of the distance from the leading edge to the trailing edge ofthe wing measured along a straight chord 21 as indicated in FIG. 5, anda similar vertical strut 22 located at a point about four-fifths of thedistance to the trailing edge measured in the same manner. The lowerends of the struts 20 and 22 are joined by horizontal tubes 23. Adiagonal brace 24 extends from the top of the strut 20 to the bottom ofthe strut 22. Other braces may be provided if desired to impartrigidity. The lower ends of the struts 2i) are braced by a U-shaped tube25 extending forwardly of the wing and the lower ends of the struts 22are joined by a similar U-shaped tube 26 extending rearwardly of thewing to provide clearance for the rider.

A support bar 27 extends between the diagonal braces 24 at a pointlocated 28% of the distance along the chord 21 from the leading edge ofthe wing as shown in FIG. 5. A seat in the form of a U-shaped tube 28 ispivoted to the support bar 27 so that a rider seated in the swingingseat always hangs vertically downwardly regardless of the pitch angle ofthe glider. are also mounted on the support bar 27 to permit a rider tosupport his weight by his hands if he so desires. A pair of braces 31and 32 extend laterally from the bottom of the strut 22 to about themidpoint of the wing spans.

A stabilizer 35 is formed by camber tubes 36 joined at their leadingends by tube 37 and at their trailing ends by a tube 38 to form aframework which is covered by a wing fabric 39 as in the case of thewing. Rudders 40 which may be formed of sheet aluminum for example arerigidly secured at the tips of the stabilizer 35. The stabilizer iscarried by tubes 41 which form an extension of the tubes 23 and bracingtubes 42 which form an extension of the center camber tubes 11 and areattached to the tubes 41 at a point in advance of the stabilizer.

The support bar 27 is located at a point so selected that the weight ofthe rider is shifted forwardly and backwardly in response to any upwardor downward tilting of the nose of the glider by an amount to produce amoment which restores the glider to the proper glide path.

It has been found that the support point should remain between one-fifthand two-fifths of the distance along the chord 21 from the leading tothe trailing edges of the wing when the attitude of the glider variesbetween 30 degrees above to 40 degrees below the normal glide angle. Forthis purpose a line 44 is drawn from a point on the camber tubeone-fifth of the distance along the chord 21 from the leading edge at arearward angle of 30 and a line 45 is drawn twofifths of the distancealong the chord 21 from the leading edge from a point on the camber tubeat a forward angle of 40. These lines are found to cross at a point 46which lies on a vertical at the 28% point in the chord 21. The supportbar 27 is positioned at this point and when so located causes the ridersweight to Straps 29 1 automatically serve as a stabilizing force tomaintain the glider on its proper glide path without requiring anycontrol on the part of the rider.

In use the water. skier carries the glider by holding the support bar 27and when he reaches the proper speed the glider will lift him from thesurface of the water. He may then seat himself in the swing seat 28 orhang from the straps 29 as he desires. He will remain aloft as long asthe towing speed is maintained and will descend when the speed isreduced. Should the towing force be interrupted as by the stopping ofthe towing boat or by the breakage or release of the towing cable theglider will immediately assume the free glide attitude and will retainthis attitude until the rider is returned to the surface of the water.Should the glider be disturbed meanwhile as by a gust of wind the ridersweight will restore it to the proper glide path within not over twohighly damped oscillations without requiring the exercise of any controlor skill on the part of the rider.

What is claimed is:

1. A glider for water skiing or the like comprising a rigid air foil anda stabilizer mounted and supported by a supporting framework to form arigid unit, a truss mounted below said framework and a transversesupport bar carried by said truss, means pivotally suspending a riderfrom said support bar, said air foil having an opening for the riderabove said support bar, said bar being located at about the intersectionof the first line drawn from a point on the air foil one-fifth of thedistance from the leading edge thereof at a rearward angle of about 30degrees to the vertical and a second line drawn from a point on the airfoil about two fifths of the distance from the leading edge thereof at aforward angle of about 40 degrees to the vertical, said point beingadapted to produce a righting moment whenever the pitch angle of theglider is disturbed from its proper glide path.

2. A glider for water skiing or the like comprising a wing composed of arigid framework of light weight tubular material and an air foilcovering said framework on both sides, said air foil being impervious towater whereby said wing is water buoyant, a stabilizer of similarconstruction rigidly attached to said wing, said stabilizer carrying apair of sheet metal fixed rudders, a truss of light weight tubingmounted below said wing and carrying a transverse support bar, means forpivotally suspcnding a rider from said support bar, said support barbeing located at about the intersection of a first line drawn from apoint on the air foil one-fifth of the distance from the leading edgethereof at a rearward angle of about 30 degrees to the vertical and asecond line drawn from a point on the air foil about two-fifths of thedistance from the leading edge thereof at a forward angle of about 49degrees to the vertical, said point being adapted to pro duce a rightingmoment Whenever the pitch angle of the glider is disturbed from itsproper glide path.

3. A glider for water skiing or the like comprising a rigid air foil, atruss rigidly fixed to said air foil and a stabilizer fixed to saidtruss rearwardly of said air foil and adapted to control the pitch angleof said air foil, a transverse support bar carried by said truss and aseat for a rider pivotally suspended from said support bar, said supportbar being located below the center of lift of said air foil and at apoint between one-fifth and two-fifths of the distance from the leadingto the trailing edges of said air foil, said point being selected andadapted to produce a righting moment for restoring the air foil to itsproper glide path whenever the pitch angle of the glider is disturbed.

References Cited in the file of this patent UNITED STATES PATENTS881,837 Whitehead Mar. 10, 1908 1,230,620 Summers June 19, 19171,233,227 Harris July 10, 1917 2,792,191 Perry May 14, 1957 OTHERREFERENCES Aerodynamics of the Airplane, Clark B. Millekan, 1941, pp.141-143 and 149.

Parade, Washington Post (Sunday edition of April 12., 1959), page 43relied on.

1. A GLIDER FOR WATER SKIING OR THE LIKE COMPRISING A RIGID AIR FOIL ANDA STABILIZER MOUNTED AND SUPPORTED BY A SUPPORTING FRAMEWORK TO FORM ARIGID UNIT, A TRUSS MOUNTED BELOW SAID FRAMEWORK AND A TRANSVERSESUPPORT BAR CARRIED BY SAID TRUSS, MEANS PIVOTALLY SUSPENDING A RIDERFROM SAID SUPPORT BAR, SAID AIR FOIL HAVING AN OPENING FOR THE RIDERABOVE SAID SUPPORT BAR, SAID BAR BEING LOCATED AT ABOUT THE INTERSECTIONOF THE FIRST LINE DRAWN FROM A POINT ON THE AIR FOIL ONE-FIFTH OF THEDISTANCE FROM THE LEADING EDGE THEREOF AT A REARWARD ANGLE OF ABOUT 30DEGREES TO THE VERTICAL AND A SECOND LINE DRAWN FROM A POINT ON THE AIRFOIL ABOUT TWO FIFTHS OF THE DISTANCE FROM THE LEADING EDGE THEREOF AT AFORWARD ANGLE OF ABOUT 40 DEGREES TO THE VERTICAL, SAID POINT BEINGADAPTED TO PRODUCE A RIGHTING MOMENT WHENEVER THE PITCH ANGLE OF THEGLIDER IS DISTURBED FROM ITS PROPER GLIDE PATH.